Brazil's premiere modern art museum has revealed that it had no insurance on paintings by Pablo Picasso and one of Brazil's best known artists, Candido Portinari, that were stolenThursday.

Eduardo Cosomano of Sao Paulo's Museum of Art said none of the museum's 8,000 works are insured: "Insuring them would be financially unviable."

The Sao Paulo Museum of Art in Brazil has unarmed guards and no alarm system to protect its collection of 8,000 works of art. ((Andre Penner/Associated Press))

Thieves broke into the museum, using only a crowbar and a car jack, making off with Picasso's Portrait of Suzanne Bloch (1904), done during his Blue Period, as well as Portinari's work depicting a coffee picker. Portinari's 1939painting, O Lavrador de Cafe,is considered one of Brazil's most iconic and valuable works of art.

Experts have pegged the Picasso'svalueat about $50 million US while the Portinari is worth about $5 million US.

"The value of the two paintings, like all the others in our collection, is incalculable and as such impossible to insure," said Cosomano.

Cosomano said the museum relied on unarmed guards patrolling the inside of the museum 24 hours a day.There are no alarms or motionsensors.

"Obviously we will now have to rethink our entire security system."

Pablo Picasso's Portrait of Suzanne Bloch, estimated to be worth $50 millon US, was one of two paintings stolen from the museum on Thursday. ((Sao Paulo Museum of Art/Associated Press))

Police say they believe the thieves were paid by a wealthy art afficianado who was adding to a private collection.

Jorge Yunes, a Sao Paulo businessman and art lover, has offered more than $55,000 US for anyone who finds and returns the paintings.

Cosomano says the museum will reopen to the public on Wednesday and confirms that two international art exhibitions will open as scheduled on Jan. 11.

The heist is similar to a bold robbery made last year in Rio de Janeiro.

A gang of five men, using a carnival street parade as cover, took four paintings by Dali, Picasso, Monet and Cezanne from the city's art museum.

The paintings, with anestimated collective value of $40 million US,have never been recovered.